I have a gold ring with 333 stamped in it what's it mean

It is more than likely the makers mark. A design code or something like that.

If the stamp is on the inside of the ring the following might help.

The stamps for percentage and karat symbol for gold expressed as follows:

333 - 8K gold
375 - 9k gold (vey popular in the old world, especially pre WWII UK)
417 - 10K gold
500 - 12K gold
585 - 14K gold
666 - 16K gold (gold teeth and fillings)
750 - 18K gold
792 - 19K gold (used in portugal)
833 - 20K
916 - 22k gold
999 - 24K gold

Very good answer above! These markings are called "hallmarks." What is quoted below is from the following site, and also supportive of the answer that has been given above. eBay Guides - Guide to Jewelry Hallmarks - History and Meaning...

Quote:

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Many European countries mark silver and gold with numerical fineness marks in thousandths, e.g. 800, 830, 900, 935, etc. for silver, 333, 500, 585, 750, 875, etc. for gold. Other symbols may be used in combination with these numbers. The British system of hallmarking is somewhat complex, but relatively easy to follow once the system is deciphered. British hallmarks include a fineness or purity mark, an assay office mark, a date letter, and usually but not always, a maker's mark.

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